Throttle body default actuation

ABSTRACT

An electronically actuated, air control valve regulates the flow of combustion air to an internal combustion engine. The valve includes an air passage having a throttle valve rotatable therein between a first, minimum air flow position and a second, maximum air flow position. Between the minimum and the maximum air flow positions is a default air flow position for operation of the engine during actuator inoperativeness. A biasing member has a first end operable to impart a force on the valve member in the direction of the default air flow position when the valve member in operable between the minimum air flow position and the default position. Likewise, the biasing member has a second end operable to impart a force on the valve member in the direction of the default air flow position when the valve member is operated in the range between the default air flow position and the maximum air flow position. As a result, a single biasing member operates to position the throttle valve at a default air flow position between the minimum and the maximum air flow positions across the entire range of positions.

TECHNICAL FIELD

The invention relates to throttle body mechanisms for internalcombustion engines and, particularly, to an apparatus for positioningthe throttle valve of an electronically actuated throttle body in adefault position allowing positive air flow therethrough.

BACKGROUND

Electronically controlled throttle valves are contemplated forcontrolling the quantity of combustion air admitted to the intakemanifold of internal combustion engines. These systems, typicallyreferred to in the automotive arts as electronic throttle controlsystems (ETC), utilize an operator-actuated pedal position sensor whichfunctions to transmit driver intent to an electronic actuator forpositioning the throttle valve. It may be desirable to mechanicallylocate the throttle valve in a predetermined "default" position at timesof actuator inoperativeness thereby assuring continued engine operation.

A contemplated apparatus for default positioning of the throttle valveutilizes a throttle valve having a range of travel extending from anegative throttle plate position through a zero or minimum throttleplate position at which air flow through the throttle valve is minimizedto a maximum or wide-open-throttle position in which air flow ismaximized. During operation of the electronic actuator, the throttleplate is operated between the minimum and maximum air flow positions.Inoperativeness of the actuator allows a biasing member to move thethrottle plate to the negative throttle plate position assuring adefault quantity of air flow to the engine and, therefore, continuedengine operation. The negative position throttle body, referred to as anover-center design, involves costly manufacturing processes imposed bythrottle bore/valve plate tolerances required to allow the throttleplate deflection through the zero or minimum air flow position.

SUMMARY OF THE PRESENT INVENTION

The present invention discloses an air control valve or throttle bodyhaving a valve which is operated by an electronic throttle actuatorbetween a minimum air flow position and a maximum air flow position.During inoperativeness of the actuator, a default mechanism positionsthe throttle valve in a default position between the minimum and themaximum positions. In the default position, positive air flow throughthe valve allows continued engine operation.

The air control valve includes a housing having an intake air passage orthrottle bore in which is disposed a throttle valve. The throttle valveis rotatable between a minimum and a maximum position to thereby meterthe quantity of air passing through the throttle bore and to the engine.The throttle valve, preferably of the butterfly type, includes athrottle plate attached to a rotatable shaft which extends diametricallyacross the throttle bore.

The throttle shaft to which the throttle plate is attached, is driven bythe electronic actuator to a desired location between the minimum andthe maximum air flow positions. As mentioned above, a default positionis located between the minimum and the maximum valve positions. It isdesirable that in all cases of actuator inoperativeness the throttlevalve be positioned in the default position to assure continued engineoperation at the default air flow. A biasing member is operable on thethrottle shaft at locations between the minimum air flow position andthe default position and at locations between the default position andthe maximum air flow position to return the throttle valve to thedefault position.

The biasing member includes a spirally wound torsion spring in a coaxialrelationship to the throttle valve shaft. The spring ends are preloadedsuch that each end exerts an opposed, rotational force on the throttlevalve shaft. A spring stop on the housing limits the travel of each endof the torsion spring such that the rotational forces exerted by the twoends of the spring member on the throttle valve shaft are only appliedto the shaft in the direction of the default throttle valve position. Assuch, during positioning of the throttle valve by the actuator, atthrottle valve locations between the minimum air flow position and thedefault air flow position, one end of the spring member exerts a forceon the throttle valve in the direction of the default position while thesecond end of the spring member is grounded against a housing stop.Should the actuator become inoperative in this range of motion, thefirst end of the spring member will return the valve to the defaultposition. Alternatively, at throttle valve locations between the defaultair flow position and the maximum air flow position, the second end ofthe spring member exerts a force on the throttle valve in the directionof the default position while the first end of the spring member isgrounded against a housing stop. Should the actuator become inoperativein this range of motion, the second end of the spring member willoperate to return the throttle valve to the default position.

As a result of the bias exerted by the first and second spring endsagainst the throttle valve shaft, the throttle valve is biased towards adefault position from all locations within it operating range. The biasof the throttle valve towards the default air flow position is achievedwith a single spring member.

Other objects and features of the invention will become apparent byreference to the following description and to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial sectional view of an air control valve assembly foran internal combustion engine embodying features of the presentinvention;

FIG. 2 is a side view of the air control valve assembly, partially insection, of FIG. 1;

FIG. 3 is a schematic view of a throttle valve, of the air control valveof FIG. 1, illustrating the range of motion of the valve;

FIGS. 4, 5 and 6 are schematic illustrations of the operation of a firstembodiment of the present invention as it is embodied in the air controlvalve assembly of FIG. 1; and

FIGS. 7, 8 and 9 are schematic illustrations of the operation of asecond embodiment of the present invention as it is embodied in the aircontrol valve assembly of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, an air control valve assembly, designated generallyas 10, is shown having a throttle body housing 12 with an air flowpassage or throttle bore 14 extending therethrough. The throttle bore 14conducts air to the intake system of an internal combustion engine (notshown). A throttle valve 16, which includes a throttle plate 18 attachedto a shaft 20, is rotatably mounted within the throttle bore 14 of thethrottle body housing 12. Bearings 22 support the throttle valve shaft20 in the housing 12 and define a throttle valve axis 24 about which thevalve 16 rotates to meter the flow of air through the throttle bore 14.FIG. 3 illustrates the full range of motion of the throttle valve 16 inthe bore 14. The valve is rotatably moveable from a minimum air flowposition "A" to a maximum air flow position "B". Intermediate of theminimum and maximum throttle valve positions is a default position "C".The default position "C" relates to a predetermined positive air flowwhich will allow continued engine operation should the actuatingmechanism used to position the throttle valve become inoperative.

Operably connected to the throttle shaft 20 is an electronic actuator26. The actuator drives the throttle valve 16, based on operator input,to position the throttle valve between the minimum "A" and the maximum"B" air flow positions.

Referring now to FIGS. 1, 2, 4 and 5, the throttle body housing 12includes a throttle return spring housing portion 28 which includes aninner wall 30 and a bottom 32 through which the end 34 of the throttlevalve shaft 20 extends for attachment to the actuator 26. A biasingmember such as spirally wound torsion spring 36 is disposed within thespring housing portion 28 of the throttle body housing 12. The spring 36surrounds the end 34 of the throttle valve shaft 20 in a coaxialrelationship therewith and includes first and second ends 38 and 40,respectively. Support for the spring coils may be provided by a bushingdisposed between the throttle shaft 20 and the coils.

The spring member 36 is rotationally preloaded within the spring housing28 by rotating the spring ends 38,40 in opposite directions about thethrottle valve axis 24 in the direction of the spring bias. The preloadof spring 36 is maintained by allowing each spring end 38,40 to abut astop 42 in the spring housing portion 28. In the embodiment shown inFIGS. 4, 5 and 6, the spring ends 38,40 abut opposite sides 44,46 of thehousing stop 42 resulting in a spring force Fa being exerted on side 44of the housing stop 42 in the counterclockwise direction, as viewed inthe Figures, of rotation about axis 24, and a spring force Fb beingexerted on side 46 of the housing stop 42 in the clockwise direction ofrotation about axis 24.

A spring actuating tang 48 depends from the throttle shaft 20 of thethrottle valve 16 and is configured for positioning between the springends 38,40 in their positions against the housing stop 42; the positionreferred to as the default throttle position "C". In the defaultposition, the throttle valve plate 18 is positioned within the throttlebore 14 to allow a positive, default quantity of air to flow to theintake of the engine allowing continued engine operation with nothrottle plate movement as in the case of actuator inoperativeness. Inthe default position "C", a neutral or zero force condition exists onthe throttle valve spring actuating tang 48 with the spring ends 38,40seated against opposing sides 44,46 of the housing stop 42 and the tang48 positioned therebetween.

During actuator operation and positioning of the throttle valve 16, theactuator 26 will rotate the throttle valve shaft 20 and attachedthrottle valve plate 18 through a range of motion extending between theminimum air flow position "A" and the maximum air flow position "B"; therange of motion including the default position "C". In the range ofmotion between the minimum air flow position "A" and the default airflow position "C", shown in FIG. 5, the first spring end 38 is moved offof its seated position against the housing stop 42. In this range ofmotion, force Fa is exerted on the spring actuating tang 48 and acts toreturn the tang to the default position "C". Actuator inoperativeness inthe range of motion between the minimum air flow position "A" and thedefault position "C" will result in the throttle valve tang 48, andassociated throttle valve 16, being moved to the default position "C"under the force Fa exerted by the spring end in the counterclockwisedirection. Once the tang 48 of the throttle shaft 20 is returned to thedefault position "C", it is prevented from moving off of the defaultposition "C" by the action of both spring ends 38,40 against the housingstop 42 and the forces Fa and Fb exerted thereon in opposing directionswhich are operable to capture the tang 48 therebetween, as shown in FIG.2. Similarly, in the range of motion between the default air flowposition "C" and the maximum air flow position "B", shown in FIG. 6, thesecond spring end 40 is moved off of its seated position against theside 46 of the housing stop 42. In this range of motion, force Fb isexerted on the valve shaft tang 48 and acts to return the tang to thedefault position "C". Actuator inoperativeness in the range of motionbetween the default air flow position "C" and the maximum air flowposition "B" will result in the throttle valve 16 being moved to thedefault position "C" under the force Fb exerted by the spring end 40 inthe clockwise direction. Similarly, once the tang 48 of the throttleshaft 20 is returned to the default position "C", it is prevented frommoving off of the default position "C" by the action of both spring ends38,40 against the housing stop 42 and the forces Fa and Fb exertedthereon in opposing directions which are operable to capture the tang 48therebetween.

It is not essential to the operation of the present invention that thefirst and second ends of the spring member be positioned against acommon housing stop as in the above example. An alternate embodiment ofthe invention, shown in FIGS. 7, 8 and 9, utilizes a throttle bodyhousing 12' having first and second housing stops 50,52 located inarcuately separated positions about the throttle valve shaft axis. Inthe preloaded state, the ends 38',40' of the spring member 36'separately engage the housing stops 50,52, respectively. The firstspring end 38' engages first housing stop 50 and exerts a force Fa inthe counterclockwise direction, as viewed in the Figures, while thesecond spring end 40' engages second housing stop 52 and exerts a forceFb in the clockwise direction. In this embodiment of the invention thedefault position of the throttle valve is defined across an arc betweenthe stops 50,52 and the spring actuation tang 48' depending from thethrottle valve shaft will similarly include the arc between itsactuating faces 54,56. Although tang 48' is illustrated as a one piecebody in the Figures, it is contemplated that multiple tangs having faces54,56 rotating in a fixed relationship to each other are equallysuitable to the present application.

During actuator operation and positioning of the throttle valve, theactuator will rotate the throttle valve through a range of motionextending between the minimum air flow position "A" and the maximum airflow position "B"; the range of motion including the default position"C". In the range of motion between the minimum air flow position "A"and the default air flow position "C", shown in FIG. 8, the first springend 38' is moved off of its seated position against the housing stop 50.In this range of motion, force Fa is exerted on the spring actuatingtang 48' and acts to return the tang to the default position "C".Actuator inoperativeness in the range of motion between the minimum airflow position "A" and the default position "C" will result in thethrottle valve tang 48', and associated throttle valve, being moved tothe default position "C" under the force Fa exerted by the spring end inthe counterclockwise direction. Once the tang 48' is returned to thedefault position "C", it is prevented from moving off of the defaultposition "C" by the action of both spring ends 38',40' against thehousing stops 50,52 and the forces Fa and Fb exerted thereon in opposingdirections which are operable to capture the tang 48' therebetween.Similarly, in the range of motion between the default air flow position"C" and the maximum air flow position "B", shown in FIG. 9, the secondspring end 40' is moved off of its seated position against the housingstop 52. In this range of motion, force Fb is exerted on the valve shafttang 48' and acts to return the tang to the default position "C".Actuator inoperativeness in the range of motion between the default airflow position "C" and the maximum air flow position "B" will result inthe throttle valve tang 48' being moved to the default position "C"under the force Fb exerted by the spring end 40' in the clockwisedirection. Similarly, once the tang 48' of the throttle shaft isreturned to the default position "C", it is prevented from moving off ofthe default position "C" by the action of both spring ends 38',40'against the housing stops 50,52 and the forces Fa and Fb exerted thereonin opposing directions which are operable to capture the tang 48'therebetween.

The disclosed invention provides an air control valve for an internalcombustion engine in which the throttle valve is positioned through anelectronic actuator. A default position providing positive air flow tothe engine is achieved through the use of a single spring member. Thethrottle default position lies between the minimum and maximum air flowpositions of the throttle valve.

The foregoing description of the preferred embodiment of the inventionhas been presented for the purpose of illustration and description. Itis not intended to be exhaustive nor is it intended to limit theinvention to the precise form disclosed. It will be apparent to thoseskilled in the art that the disclosed embodiments may be modified inlight of the above teachings. The embodiments described were chosen toprovide an illustration of the principles of the invention and itspractical application to thereby enable one of ordinary skill in the artto utilize the invention in various embodiments and with variousmodifications as are suited to the particular use contemplated.Therefore, the foregoing description is to be considered exemplary,rather than limiting, and the true scope of the invention is thatdescribed in the following claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. An air control valve foran internal combustion engine comprising a housing having an air intakepassage extending therethrough with a throttle valve rotatably mountedin said passage, said throttle valve rotatable about an axis within arange of rotation between a first, minimum air flow position and asecond, maximum air flow position, said range including a defaultposition intermediate of said minimum and said maximum air flowpositions of said valve, a spring member having a first end operable toimpart a force on said valve, in the direction of said default position,when said valve is between said first, minimum air flow position andsaid default air flow position, and a second end operable to impart aforce on said valve, in the direction of said default position, whensaid valve is between said default air flow position and said maximumair flow position, said first and second ends of said spring memberoperable to return said valve to said default position through saidrange of rotation.
 2. An air control valve for metering air to aninternal combustion engine comprising a housing having an air intakepassage extending therethrough with a throttle valve rotatably mountedin said passage, said throttle valve rotatable about an axis within arange between a first, minimum air flow position and a second, maximumair flow position, said range including a default position intermediateof said minimum and said maximum air flow positions of said valve, aspiral-wound torsion spring located coaxially about said throttle valveaxis, having a first end operable to impart a force on said valve, inthe direction of said default position, when said valve is between saidfirst, minimum air flow position and said default air flow position, anda second end operable to impart a force on said valve, in the directionof said default position, when said valve is between said default airflow position and said maximum air flow position, said first and secondends of said spring member operable to return said valve to said defaultposition through said range.
 3. An air control valve for metering air toan internal combustion engine comprising a housing having an air intakepassage extending therethrough with a throttle valve rotatably mountedin said passage, said throttle valve rotatable about an axis within arange of rotation between a first, minimum air flow position and asecond, maximum air flow position, said range including a defaultposition intermediate of said minimum and said maximum air flowpositions of said valve, a spiral-wound torsion spring member locatedcoaxially about said throttle valve axis, having a first end operable toimpart a force on said valve, in the direction of said default position,and a second end operable to ground against a stop, fixed relative tosaid housing, when said valve is between said first, minimum air flowposition and said default air flow position, and said second endoperable to impart a force on said valve, in the direction of saiddefault position, and said first end operable to ground against saidstop, fixed relative to said housing, when said valve is between saiddefault air flow position and said maximum air flow position, said firstand second ends of said spring member operable to return said valve tosaid default position through said range of rotation.
 4. An air controlvalve for metering combustion air to an internal combustion enginecomprising a throttle housing having an air passage extendingtherethrough, a throttle valve mounted for rotation in said air passageto vary the flow of air therethrough, said valve comprising a throttleplate mounted on a shaft rotatable about an axis, said valvepositionable within a range between a first, minimum air flow positionand a second, maximum air flow position, said range including a defaultposition intermediate of said minimum and said maximum positions, aspirally wound torsion spring disposed in a coaxial relationship to saidthrottle valve shaft, said spring member having a first end locatedadjacent a first stop face and imparting a first force thereon in afirst direction and a second end located adjacent a second stop face andimparting a second force thereon, opposing said force from said firstspring end, said throttle valve shaft having a spring actuator dependingtherefrom and rotatable therewith, said actuator positioned between saidfirst and said second stop faces to locate said shaft and said throttlevalve in said default air flow position, and operable to move said firstspring end off of said first stop face, against said first force, assaid throttle valve moves between said minimum air flow position andsaid default air flow position, and operable to move said second springend off of said second stop face, against said second opposing force, assaid throttle valve moves between said default air flow position andsaid maximum air flow position, said first and said second forcesoperable to return said throttle spring actuator to said locationintermediate of said first and said second stop faces to thereby returnsaid throttle valve to said default air flow position throughout saidthrottle valve range.